As I explain with magisterial force and eloquence in the comment box to this Inside Catholic article. While important and decisive in its own way, the battle of Lepanto didn't "save Europe" any more than the Battle of Midway "saved America."
That's not a function of the particular battle between Don Juan and the Sultan: rather, it's just the way naval battles go. Boots on the ground decide the matter, not rudders in the water.
Feel free to brickbat away!